Flushing the stream will not flush its underlying encoder unless you explicitly call an implementation of Flush or Close. Setting AutoFlush to true means that data will be flushed from the buffer to the stream, but the encoder state will not be flushed. This allows the encoder to keep its state (partial characters) so that it can encode the next block of characters correctly. This scenario affects UTF8 and UTF7 where certain characters can be encoded only after the encoder receives the adjacent character or characters.

A call to Close is required for proper operation of a stream. Following a call to Close, other operations on the stream could throw exceptions. If the stream is already closed, a call to Close throws no exceptions.